System and device for avoiding any change of the cross section of tubular bodies during their cold bending

ABSTRACT

A bending mandrel for pipe comprises a flat elongated body having a pair of terminal members joined by a pair of shanks defining a longitudinal extending slot, the shanks being of progressively increasing cross-section toward the midpoint whereby, upon insertion of the mandrel into the pipe to be bent, the shanks are squeezed together and at the midpoint approach one another while conforming to the width of the pipe.

United States Patent 1191 Crotti [4 Jan.- 14, 1975 SYSTEM AND DEVICE FOR AVOIDING 2,729,265 1/1956 Jones 72/478 gg iif gg ig gg figg ESE Q OF FOREIGN PATENTS 0R APPLICATIONS BENDING IR C LD 55,437 6/1936 Norway 72/150 90,113 11/1922 Germany 72/466 [75] Inventor; Pieru Crofli, Bologna It ly 158,189 10/1962 U.S.S.R......... 72/466 18,092 6/1956 Germany 1 72/466 Asslgneer Camar 1,527,410 10/1970 Germany 72/370 Roveredo/Graubunden, Switzerland 22] il J 9, 1973 Primary ExaminerC. W. Lanham Assistant Examiner-E. M. Combs [21] Appl' 377,732 Attorney, Agent, or Firm-Karl F. Ross; Herbert Dubno [30] Foreign Application Priority Data Sept 18, 1972 Italy 52811/72 [57] ABSTRACT Y A bending mandrel for pipe comprises a flat elongated [:2] :LS. C!l. 72/465 body having a pair of terminal members joined by a B211] 9/01 p of Shanks defining a longitudimal extending Slot, 1 0 72/ the shanks being of progressively increasing cross- 72/465 14 section toward the midpoint whereby, upon insertion 56 f of the mandrel into the pipe to be bent, the shanks are 1 Re erences C'ted squeezed together and at the midpoint approach one UNITED STATES PATENTS another while conforming to the width of the pipe. 179,130 6/1876 Orum 72/466' 1 Cl 5 D F. 425,395 4/1890 Wingate et a1...... 72/466 gums SYSTEM AND DEVICE FOR AVOIDING ANY CHANGE OF THE CROSS SECTION OF TUBULAR BODIES DURING THEIR COLD BENDING The present invention relates to a pipe-bending mandrel.

According to the invention, a pipe-bending mandrel or core, preferably molded from a synthetic resin such as polyethylene or nylon, has a flattened elongated configuration and consists of a pair of terminal members interconnected by longitudinally extending shanks which define a longitudinally extending throughgoing slot between them. In the relaxed condition of the device, the slot is defined between parallel walls of the shanks while the shanks are of increasing cross-section from their terminal members to the center so that, upon insertion of the mandrel into the pipe, the shanks are deflected inwardly and at the bend lie almost in abutting relationship so that the solid width of the deformed mandrel at its center substantially equals the corresponding width of the pipe.

The invention is further described with reference to the accompanying drawing in which:

FIG. 1 is an elevational view of the device in its relaxed position;

FIG. 2 is a longitudinal section taken along the line A A of FIG. 1;

FIG. 3 shows the device in elevation as it is about to be inserted into a pipe;

FIG. 4 is a view of the pipe in section with the device fully inserted and the shanks compressed; and

FIG. 5 is a section similar to FIG. 2 through the bent pipe with the device in place.

In the drawing, I have shown a bending mandrel which comprises a pair of terminal members 3a of rectangular configuration, bridged by a pair of shanks 3 which define a longitudinal slot 4 between them. The inner faces of the shanks, defining the slot, are parallel as can be seen in FIG. 1 while the outer walls are tapered toward the ends of the mandrel l to impart the progressively increasing cross-section to the shanks to the center plane B B which lies transversely to the longitudinal dimension of the device.

The mandrel 1, being flattened as may be seen from FIGS. 1 and 2, can be readily bent from the longitudinal plane C C, but resists bending within this plane.

From FIGS. 3 and 4, it may be seen that the mandrel 1 has a relaxed width at its center plane B B which exceeds the internal diameter or width of the pipe 2 into which it is to be inserted, but a terminal width which may be slightly less than this diameter to permit ease of insertion.

When fully inserted, the central plane B B lies at the bend and the shanks are bowed inwardly substantially into contact with one another so that the solid compressed width of the mandrel is approximately equal to the corresponding dimension of the tube. The tube may now be bent (FIG. 5) without collapse of the pipe (see FIG. 5).

I claim:

1. A pipe-bending mandrel receivable in a pipe of a predetermined diameter to permit bending thereof without collapse, said mandrel comprising a flat elongated body having a pair of terminal members of a width less than said diameter, and] a pair of elongated shanks interconnecting said members and defining between them a longitudinally-extended throughgoing slot, said shanks having inner parallel walls defining said slot in a relaxed position of said body outside said pipe, but being of increasing cross-section from said members toward the center of said body whereby upon inward deflection of said shanks, the solid width of said body at said center corresponds substantially to the diameter of said pipe, the width of said body in a relaxed condition thereof external of said. pipe being greater than said diameter at said center. 

1. A pipe-bending mandrel receivable in a pipe of a predetermined diameter to permit bending thereof without collapse, said mandrel comprising A flat elongated body having a pair of terminal members of a width less than said diameter, and a pair of elongated shanks interconnecting said members and defining between them a longitudinally-extended throughgoing slot, said shanks having inner parallel walls defining said slot in a relaxed position of said body outside said pipe, but being of increasing cross-section from said members toward the center of said body whereby upon inward deflection of said shanks, the solid width of said body at said center corresponds substantially to the diameter of said pipe, the width of said body in a relaxed condition thereof external of said pipe being greater than said diameter at said center. 